Between the hamster wheel grind at work, the commute to and from, fatigue, on the open road can seem like an accepted fact of modn life. In fact an estimated 250,000 americans drive drowsy every day, and that can turn into a very real nightmare, so the next time you find yourself with miles to go before you sleep, something to think about. From abc's ron claiborne. Reporter: The video is shocking. A woman driving a car in denver asleep at the wheel. Watch as she drifts in and out of her line, somehow she never crashes. She drove 30 miles before a police car was finally able to pull her over. About 6800 drivers each year aren't so lucky. They fall asleep while driving, crash and die. Drowsy driving is the second-leading cause of fatal vehicle accidents behind only drunk driving and ahead of driving while texting. It's not just driving that is affected. A recent study in the journal of american medical association estimated that workplace accidents from sleep deprivation cost $31 billion of damage every year. Sleep is such a powerful drive that if you really need it, the brain is going to say, sleep. And that can be an incredibly dangerous situation. Reporter: But it's driving while sleeping that is especially harrowing. Some drowsy drivers experience a phenomenon you probably never heard of called micro sleep where you fall asleep for just a few seconds without realizing it. I volunteered to be the guinea pig, to see how I would be affected without enough sleep. First I stayed up 32 consecutive hours. I've hit the proverbial wall. I'm ron claiborne. I traveled to the liberty mutual research institute outside boston when this study the effects of sleep deprivation on driving. It can happen in the blink of an eye. Reporter: Chronic lack of sleep fogs the mind, makes people more likely to make mistakes at school or work. It makes us emotionally volatile and more prone to illness. At the research lab I was hooked up to a brain wave monitor and a device that tracks eye movement. I feel okay now. But not great. Then I got behind the wheel of a minivan. As tired as I was, I thought i would be okay. We'll see. I feel like I can drive pretty well. Then, I started driving on a closed track with a researcher sitting next to me who could step on an emergency brake if things went awry. I'm feeling pretty worn out. Soon I was becoming sleepier and sleepier, it became a struggle to keep my eyes open and hold my head up. Before long I was experiencing micro sleep. I looked like a normal wake driver but you can't tell that my brain is actually asleep. Half hour in it became more obvious. I had fallen asleep at the wheel and driven completely off the road. That was nod got good. I soon realized I just couldn't go on. I'm done. Put it in park then. Good idea. It was too dangerous. That was tough. Back in the lab, they showed me what was going on inside my brain while I was driving. This is evidence you're falling asleep. Reporter: My eyes were open but see how the lines are becoming more jagged? That's sleep coming on. And these lines, show my blinking is getting slower. What about when I drove off the road? We could see it coming in your brain waves. Reporter: Looking at the chart here how long was my micro sleep? In this one episode? In this one episode we're talk about one, two, three, four, five or six seconds. Reporter: What was most shocking, the doctor said I fell asleep, I micro slept 21 other times. You had dozens of times where your eyes began rolling around in their sockets, this would happen two, three, four seconds, couple of good rolls. Reporter: If I had been drividrive ing 60 miles an hour I would have gone the length of a football field asleep. Then you would come to and keep driving. Reporter: I'd remembered none of them. Fortunately I had been in a hi highly controlled situation with safety precautions, driving 20 to 30 miles an hour. Thousands of sleep deprived americans at 60 miles an hour convinced, as I was, that they can outrace their own fatigue. I was in a real twilight zone the entire time. And it was scary. For "nightline," ron claiborne in massachusetts.

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